On the first 6 exams of his history class, Ishaan got an average score of 84. What does he need on the next exam to have an overall average of 86?
Explanation: Let his score on the next exam be $x$ The sum of all of his scores is then $6 \cdot 84 + x$ The same sum must also be equal to $7 \cdot 86$ Solve: $x = 7 \cdot 86 - 6 \cdot 84 = 98$.